Ceiling mounted fans are often used for circulating air within large buildings such as warehouses, factories, gymnasiums, churches, auditoriums, convention centers, theaters, and other buildings with large open areas. For fire safety, a matrix of overhead sprinklers are usually installed to quench fires that might occur within the building. In the event of a fire, the fans preferably are disabled and the sprinklers are turned on.
To detect a fire and control the operation of the fans and sprinklers appropriately, various types of fire sensors are available. They usually operate by optical detection (photoelectric), chemical reaction (ionization), or heat detection (fusible link or infrared sensor for radiation).
Even though a ceiling fan can be de-energized during a fire, various air currents within the building or spray from a nearby sprinkler might keep the fan slowly rotating. Depending on the design of the fan, if the fan blades repeatedly pass underneath and/or come to stop underneath an activated sprinkler head, the fan blades might create interference with the water or other fire-suppressing media spraying from the sprinkler.